Magnetomotive Force (MMF)

Magnetomotive Force (MMF)

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Magnetomotive Force (MMF)

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Gilbert is a unit of (a) electromotive force (6) magnetomotive force (c) conductance (d) permittivity

Description : Gilbert is a unit of (a) electromotive force (6) magnetomotive force (c) conductance (d) permittivity

Last Answer : (6) magnetomotive force

Magnetomotive force formula

Description : Magnetomotive force formula

Last Answer : Magnetomotive force formula

What is magnetomotive force?

Last Answer : Mmf is a force that drives magnetic flux in a magnetic circuit.

What is the full form of MMF ?

Last Answer : MMF - Synthetic Music Mobile Application File

What is the full form of MMF ?

Last Answer : Synthetic Music Mobile Application File

Why is the MMF method of estimating the voltage regulation considered as the optimistic method?

Description : Why is the MMF method of estimating the voltage regulation considered as the optimistic method?

Last Answer : In this method the actual value is more than the result obtained.

What are the test data required for predetermining the voltage regulation of an Alternator by MMF method?

Description : What are the test data required for predetermining the voltage regulation of an Alternator by MMF method?

Last Answer : Data required for MMF method are : · Effective resistance per phase of the 3-phase winding R · Open circuit characteristic (OCC) at rated speed/frequency · Short circuit characteristic (SCC) at rated speed/frequency

Which of the following relations is correct? a) MMF = ∫ B.dl b) MMF = ∫ H.dl c) EMF = ∫ E.dl d) EMF = ∫ D.dl

Description : Which of the following relations is correct? a) MMF = ∫ B.dl b) MMF = ∫ H.dl c) EMF = ∫ E.dl d) EMF = ∫ D.dl

Last Answer : c) EMF = ∫ E.dl

The line integral of the electric field intensity is a) Mmf b) Emf c) Electric potential d) Magnetic potential

Description : The line integral of the electric field intensity is a) Mmf b) Emf c) Electric potential d) Magnetic potential

Last Answer : b) Emf

Calculate the reluctance of the material with a mmf of 3.5 units and flux of 7units. a) 32.5 b) 10.5 c) 0.5 d) 2

Description : Calculate the reluctance of the material with a mmf of 3.5 units and flux of 7units. a) 32.5 b) 10.5 c) 0.5 d) 2

Last Answer : b) 10.5

In a 3-phase synchronous motor (A) the speed of stator MMF is always more than that of rotor MMF. (B) the speed of stator MMF is always less than that of rotor MMF. (C) the speed of stator MMF is synchronous speed while that of rotor MMF is zero. (D) rotor and stator MMF are stationary with respect to each other.

Description : In a 3-phase synchronous motor (A) the speed of stator MMF is always more than that of rotor MMF. (B) the speed of stator MMF is always less than that of rotor MMF. (C) the speed of ... speed while that of rotor MMF is zero. (D) rotor and stator MMF are stationary with respect to each other.

Last Answer : Ans: D Because, Motor is magnetically locked into position with stator, the rotor poles are engaged with stator poles and both run synchronously in same direction Therefore, rotor & stator mmf are stationary w.r.t each other.

In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.

Description : In a d.c. machine, the armature mmf is (A) stationary w.r.t. armature. (B) rotating w.r.t. field. (C) stationary w.r.t. field. (D) rotating w.r.t. brushes.

Last Answer : (C) stationary w.r.t. field.

In D.C. machines, the ____ in field mmf results in increase in size and cost of machines. (a) increase (b) decrease (c) either of the above (d) none of the above

Description : In D.C. machines, the ____ in field mmf results in increase in size and cost of machines. (a) increase (b) decrease (c) either of the above (d) none of the above

Last Answer : (a) increase

In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made (a) equal to that of armature mmf (b) less in comparison with the arma¬ture mmf (c) large in comparison with the arma-ture mmf (d) none of the above

Description : In D.C. machines, ir order to prevent excessive distortion of field form by the armature reaction, the field mmf must be made (a) equal to that of armature mmf (b) less in comparison with the arma¬ture mmf (c) large in comparison with the arma-ture mmf (d) none of the above

Last Answer : (c) large in comparison with the arma-ture mmf

(a) Define permeability. (b) Define MMF. (c) Define form factor of an alternating quantity. (d) Define frequency and time period of an alternating quality. (e) Define transformation ratio of transformer. (f) State the EMF equation of a 1 transformer and state the meaning of each term used. (g) Give two applications of single phase motors.

Description : (a) Define permeability. (b) Define MMF. (c) Define form factor of an alternating quantity. (d) Define frequency and time period of an alternating quality. (e) Define transformation ratio of transformer. ... and state the meaning of each term used. (g) Give two applications of single phase motors. 

Last Answer : Permeability : It is the ability of a magnetic/Non magnetic material to allow setting up of flux in it.  MMF : The magneto motive force (MMF) is the force required to setup flux in a magnetic / ... applications of single phase motors : Water pumps, ceiling fan, lathe machine

Define : i) MMF ii) Reluctance iii) Fringing iv) Leakage flux

Description : Define : i) MMF ii) Reluctance iii) Fringing iv) Leakage flux

Last Answer : i) MMF:  It is the force that drives magnetic flux through magnetic circuit. It is measured in amp-turns.  ii) Reluctance (s) :-  Reluctance is the property of the substance ... through the magnetic circuit, leaks through the air surrounding the core. This flux is called as leakage flux.

Define MMF and state its unit.

Description : Define MMF and state its unit.

Last Answer : M.M.F. stands for magnetomotive force. M.M.F. is the force behind the flow of magnetic flux. MMF is defined as the force behind the flow of magnetic flux or production of magnetic flux is called as ... ampere and unit for number of turns is turns. So the unit for M.M.F. is ampere turns.

The stator mmf and rotor mmf of a 3-phase induction motor

Description : The stator mmf and rotor mmf of a 3-phase induction motor (A) are equal (B) rotate with slip speed (C) are opposite but rotate with synchronous speed (D) rotate with the same rotor speed 

Last Answer : a

The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction

Description : The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction machine is  (A) 107.14 rpm in forward direction (B) 107.14 rpm in reverse direction (C) 5250 rpm in forward direction (D) 5250 rpm in reverse direction

Last Answer : The synchronous speed for the seventh space harmonic mmf wave of a 3-phase, 8-pole, 50 Hz induction machine is 107.14 rpm in forward direction 

State Lenz’s law.

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Last Answer : Lenz’s Law: It states that the direction of electromagnetically induced emf is such that it always opposes the main cause of its production. Or It is expressed by equation E = - N (dΦ/dt) volts Where – sign indicate the direction EMF is induced opposite to rate of change of flux. 

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